Cosmetic formulating techniques have grown over the years due to a large variety and number of new raw material introductions. One of the changes over the last 25 years is the widespread use of cyclosiloxanes. These cyclic silicones have a number of properties that make them well suited for cosmetic formulating, including their volatility and aesthetic application properties. All varieties of cosmetic and personal care products have utilized these cyclic silicones to their advantage, such as creams and lotions, color cosmetics, hair care products and antiperspirants.
Recently, there have been safety concerns over cyclotetrasiloxanes (also called D4, or octamethylcyclotetrasiloxane) resulting in the removal of that chemical from most, if not all, formulations. Cyclopentasiloxane (also called D5 or decamethylcyclopentasiloxane) subsequently replaced D4 in formulations. Examples of D5 products include Dow Corning's DC 245 Fluid, and GE's SF 1202.
The structures of D4 and D5 are very similar, but the volatility rate of the D5 is not as high as the D4. Currently, the D5 is now also coming under scrutiny, and many formulators are being proactive and looking for a substitute product now, such as a silicone-free product, in the event D5 is to be removed from formulations.
Purified hydrocarbons, such as Isododecane (Permethyl® 99A) have been tried, but do not exhibit the same aesthetic properties as do the volatile silicones. Some companies have tried combinations of hydrocarbons to achieve a suitable volatility, but when the desired volatility is reached, these products still do not exhibit the required aesthetics, i.e., the feel on the skin, during application.